Reliable synchronizing application

I am a freelance video editor. I do most of my work at home on a MacPro, however at least 3 times a week I go to client's locations with mobile editing setup and work there. I copy the project folder to an external hard drive before going to the location, and when I come back I have to copy the project file from my mobile drive back to the MacPro, overwriting the old one. Some project folders get as high as 100GB, so copying all the files is time consuming. I used to synchronize the project folders on the desktop system and the mobile drive using Retrospect on the old G4 system, however Retrospect remains a PowerPC application (with the exception of their client software), which I can no longer rely on.

Is there a universal reliable software out there for synchronizing? The projects I am working on are extremely important, so it has to be a rock solid application with a good reputation. I cannot seem to find anything convincing. Thanks guys.